ANCESTORS 'USED DRUGS TO SURVIVE'

Mind-altering drugs may be so popular because they were once used by our
ancestors to survive, two leading anthropologists have argued. Dr Roger
Sullivan, of the University of Auckland, and Edward Hagen, of the
University of California at Santa Barbara, say there is plenty of evidence
that humans have sought out so-called psychotropic drugs over millions of
years.

These plants are rich in alkaline substances such as nicotine and cocaine
that produce a stimulant effect and may have helped to make life bearable
in the most harsh of environments.

For example, until recently Australian Aborigines used the nicotine-rich
plant pituri to help them endure desert travel without food. And Andeans
still chew coca leaves to help them work at high altitudes.

Archaeological evidence shows that drug use was widespread in ancient cultures.

Betel nut, for example, was chewed at least 13,000 years ago in Timor, to
the north of Australia. Artefacts date the use of coca in Ecuador to at
least 5,000 years ago.

Ancient 'Freebasing'

Many of these substances were potent: pituri contains up to 5% nicotine -
tobacco today contains about 1.5%.

What is more, these drug pioneers sometimes 'freebased' drugs by chewing
them together with an alkali such as lime or wood ash.

This releases the free form of the drug and allows it to be directly
absorbed into the bloodstream.

However, Dr Sullivan said that in Pacific cultures where chewing betel nut
is still widespread, it is seen more as a source of food and energy than as
a drug.

Some drugs do have real nutritional value. For example, 100 grams of coca
leaf contains more than the US recommended daily intake of calcium,
phosphorus, iron and vitamins A, B2 and E.

Brain function Dr Sullivan and Dr Hagen believe that eating psychotropic
plants may also have played an important role in helping the brain to
function properly.

They argue that in some particularly tough environments, people's diets may
have been so poor that they struggled to produce enough chemicals to help
the brain function normally.

Consuming plants containing substances that mimic the role of these
chemicals could have helped make up for the shortfall.

Dr Wayne Hall, of the University of Queensland, who until recently was head
of the National Drug and Alcohol Research Centre in Sydney, said the theory
was certainly plausible.

He said: "There is certainly evidence that plants evolved to mimic the
neurotransmitters of mammals.

"But the problem today is that we have much larger doses of much more
purified drugs."

Professor Tonmoy Sharma, a consultant psychiatrist at Stonehouse Hospital,
Dartford, told BBC News Online that modern drug taking was more likely to
be related to peer pressure.

He said: "Historically speaking a lot of people who did abuse drugs seem to
be from the higher socio-economic classes who had relative luxuries in
their lives.

"A lot of people who take drugs are not necessarily getting rid of their
problems. It is more a question of fitting into a certain social grouping."